Quenching oil and method of quenching metals



United States Patent 3,113,054 QUENCHING OIL AND METHOD OF QUENCHINGMETALS Michael George Billett and James Gibson, both offinnbury-on-Thames, England, assignors to The British Petroleum CompanyLimited, London, England, a British joint-stock corporation No Drawing.Filed Mar. 17, 1961, Ser. No. 96,394 Claims priority, application GreatBritain Mar. 18, 1960 6 Claims. (Cl. 14829) Many metal alloys,especially ferrous alloys, require a heat treatment (e.g. at atemperature of 850 C.) followed by rapid cooling to develop thenecessary degree of hardness. The hardness of an alloy is mainlydependent upon the formation of a certain physical structure; in thecase of steel, the hardness is determined by the proportion ofmartensite formed during the hardening process. Rapid cooling of thealloy is usually effected by immersing the hot alloy in a relativelycool quenching liquid. A commonly used quenching liquid is mineral oilbut for certain alloys, e.g. high-carbon, low-alloy steels straightmineral oils do not form satisfactory quenchants since the initial rateof cooling is too slow. A faster initial cooling rate can be obtained byusing Water as the quenching medium but this is unsatisfactory for largesections since it cools the metal too quickly at the lower temperaturesand often results in distortion and cracking.

We have now developed an improved quenching oil and method of quenchingalloys which is particularly suitable in the case of high-carbon,low-alloy steels and other alloys which cannot be satisfactorily cooledin straight mineral oil.

According to the invention there is provided a method of quenchingalloys in which there is used a quenching oil consisting of alubricating oil base containing dissolved therein a small amount of anoil-soluble aluminium compound. (The term oil-soluble is used in thesense that the compound must be capable of remaining in stablesuspension in the oil and not separate out of storage. Thus the compoundmay be present in the oil in the form of a colloidal suspension.)

The lubricating oil is preferably a refined mineral lubbricating oilobtained from the distillation of crude petroleum particularly onehaving a hash point above 350 F. and a Redwood I viscosity at 140 P. notgreater than 100 seconds. The viscosity of the quenching oil should alsopreferably not exceed 100 seconds, e.g. 3075 seconds, Redwood I at 140F. If the aluminium compound has a tendency to thicken the lubricatingoil, this may be counteracted by the use of an anti-gelling agent eg 8-hydroxyquinoline.

The amount of the oil-soluble aluminium compound dissolved in thelubricating oil base is preferably not greater than 10%, e.g. 0.5%, byWeight of the final composition.

A preferred class of aluminium compounds are the polyoxo-aluminiumacyla-tes. These compounds may be prepared by heating aluminiumalcoholates with water and carboxylic acids in one or more stages andpreferably in an inert, non-volatile diluent such as a light lubricatingoil. This method of preparation is described in UK. patent specification825,878. Another method of preparation is to heat aluminium alooholateswith carboxylic acids alone so as to liberate alcohol and form acyloxyaluminium alcoholate compounds, and further heat the latter compounds.This method of preparation is described in UK. patent specification806,113. Examples of such polyoxo-aluminium acylates are those havingthe average general formula (OAlX) where n is an integer greater than 1,preferably 210, and X is an acylate group,

3,1 13,054 Patented Dec. 3, 1963 i.e. a group having the formula RCOO-where R is an aliphatic or aromatic hydrocarbon or substitutedhydrocarbon radical, especially a saturated or unsaturated alkyl or arylradical containing 630 carbon atoms. Particularly preferred are suchcompounds in which the acylate groups are derived from benzoic orsalicyclic acids, or aliphatic monocarboxylic acids having 12-20 carbonatoms, e.g. stearic or oleic acids. It is to be understood that theacylate groups in any given molecule of the additive may be the same ordifferent and that the additive may consist of a mixture of differentmolecules.

Another suit-able class of oil soluble aluminium compounds are thealuminium glycolates.

The invention also consists in a quenching oil consisting essentially ofa lubricating oil having a flash point above 350 F. and a Redwood Iviscosity at 140 F. of not more than seconds, e.g. 3075 seconds,preferably a mineral lubricating oil obtained from the distillation ofpetroleum, and containing dissolved therein 0.5-5 by weight of the totalquenching oil of an oil soluble alu minium compound, particularly one ormore of the preferred types of aluminium compound hereinbeforespecified, the viscosity of the quenching oil being not greater than 100seconds Redwood I at F., e.g. 3075 seconds.

A number of examples of the invention will now be described.

EXAMPLE 1 A hardness test was carried out of samples of tile steel (21low alloy steel containing 1.23% weight carbon) which had been quenchedin a straight mineral lubricating oil and in a quenching oil accordingto the invention made using the same lubricating oil.

The straight mineral lubricating oil (hereinafter called oil L) wasobtained from the vacuum distillation of a Middle Eastern crudepetroleum oil and had had the normal refining treatment viz dewaxing,solvent refining with furfural, and clay treatment. The refined oil hada Redwood I viscosity at 140 F. of 50 seconds, and a flash point of 400F.

The quenching oil according to the invention (hereinafter called oil Q1)was made by adding 3% by weight of an oil soluble compound M to theabove lubricating oil. The aluminium compound M was one commerciallyavailable under the trade name Manalox and had been prepared as follows:

One molecular proportion of aluminium isopropoxide was reacted with twomolecular proportions of commcroial oleic acid at a temperatureincreasing to about 220 C. Two molecular proportions of isopropanoldistilled off during the reaction a slight vacuum being ap plied nearthe end to aid the removal of the last traces of isopropanol. It isbelieved that the product (M) consisted of a solution in one part byweight of isopropyl oleate of one part by weight of a polyoxo-aluminiumacylate of the general formula (OAlGOCRQ where R is an oleyl radical,and n is 210 predominantly 3.

Samples of the file steel 0.3" X 1.4" X 4.5" in size were heated forhalf an hour at 800 C. in an electric furnace and then quenched byplunging them into 5 gallons of the quenchant at room temperature. Thequenched samples were then parted slightly off centre on a water cooledslitting wheel giving a transverse section which was ground back to acentre line, polished and then hardnesstested using the well-knownVickers hardness tester. The hardness transverse was made at 0.1"intervals along a line running centrally across the section parallel toits two longer sides. All tests were done in duplicate. The results aregiven in the following table.

It will be seen that the use of the quenching oil according to theinvention gave a product of much more uniform hardness across itssection as compared with the use of the base oil.

EXAMPLE 2 The initial cooling rate of oils Q1 and L and of an oil (Z)sold commercially as a fast quenching oil, were detcrmined by a nickelball test. In this test use is made of the well known property of metalsin that they lose their magnetism when heated above a certaintemperature (the Curie point) which is characteristic for each metal.Nickel was chosen for these quenching tests because of its non-scalingcharacteristics and resistance to cracking during quenching. The testprocedure consisted essentially of heating a nickel ball to 850 C. in atube furnace then quenching in the oil. The time for the ball to be comemagnetic gave an accurate measure of the speed of quench from 850 C. to354 C. (the Curie point of nickel). The results were as follows:

Seconds Oil Q1 15.5 Oil L 22.7 Oil Z 19.3

It will be seen that from the point of view of fast initial coolingrate, the quenching oil according to the invention was the best of theoils tested.

EXAMPLE 3 Some chain links of various sizes made from chromenickel steelcontaining 0.40.5% weight C, 1.2% weight r Ni and 1.8% weight Cr werequenched in the straight mineral lubricating oil L referred to above andin a quenching oil according to the invention (Q2) made by dissolving 5%by weight (based on the final composition) of compound M in lubricatingoil L. The quenching system consisted of a continuous conveyor whichtook the links through a furnace maintained at 850 C. where theyremained for approximately minutes before dropping a distance of 1 footinto the quenching bath maintained at 60 C. Rockwell C hardness tests onthe treated links showed that in the smaller links (approximately /2inch 4 long) an increase in surface hardness of 15% was achieved usingoil Q2 as compared with when oil L was used. For the larger links (12inches long, 4 inches wide, /2 inch thick) an increase in surfacehardness of 10% was achieved. Some of the smaller links were sectionedand an even hardness distribution was found to exist through thesection.

EXAMPLE 4 Some silicon-manganese spring steel stampings (for arefrigerator temperature controller) having a carbon content from 0.6 to0.7% weight were quenched in the straight mineral lubricating :oil L andin the quenching oil according to the invention, Q2. The stampings werepassed in an atmosphere of hydrogen through an electrically heatedfurnace maintained at 900 C. and were discharged into a tank ofquenching oil mounted beneath the furnace. The tank contained 40 gallonsof oil at a temperature of 6070 C. When quenching in oil L, a hardnessof 530670 V.P.N. (Vickers pyramid number) was obtained. With oil Q2,hardness values of the order of 750 V.P.N. were obtained, which wassimilar to that obtained by quenching the steel stampings in water.

We claim:

1. A method of quenching alloys in which there is used a quenching oilconsisting of a mineral lubricating oil base containing dissolvedtherein an oil soluble polyoxoaluminium acylate compound having theaverage general formula (OAlX) where n is 2-10 and X is an acylate groupof the formula RCOO where R is a hydrocarbon radical containing 6-30carbon atoms, in an amount sufiicient to increase the initial rate ofcooling of said lubricating oil base.

2. A method according to claim 1, in which the lubricating oil is arefined mineral lubricating oil obtained from the distillation of crudepetroleum.

3. A method according to claim 2, in which the lubricating oil has aflash point above 350 F. and a Redwood I viscosity at 140 F. of up toseconds.

4. A method according to claim 1, in which the amount of the oil solublealuminium compound dissolved in the lubricating oil is 0.5-5% by weightof the quenching oil.

5. A method according to claim 1, in which the acylate groups in thepolyoxo-aluminium acylate are derived from at least one of the followingacids: benzoic acid, salicylic acid and aliphatic monocarboxylic acidshaving 12-20 carbon atoms.

6. A method according to claim 1, in which the amount of the oil solublealuminium compound dissolved in said lubricating oil base is not greaterthan 10% by weight.

References Cited in the file of this patent UNITED STATES PATENTS2,202,364 Wiezevich May 28, 1940 2,744,074 Theobald May 1, 19562,848,362 Flemmert et al. Aug. 19, 1958 2,925,430 Stedehouder et al Feb.16, 1960 3,054,816 Rinse Sept. 18, 1962 FOREIGN PATENTS 825.878 GreatBritain Dec. 23, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,113,054 December 3, 1963 Michael George Billettet a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1 line 39, for "separate out of storage" read separate out onstorage Signed and sealed this 28th day of April 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A METHOD OF QUENCHING ALLOYS IN WHICH THERE IS USED A QUENCHING OILCONSISTING OF A MINERAL LUBRICATING OIL BASE CONTAINING DISSOLVEDTHEREIN AN OIL SOLUBLE POLYOXOALUMINUM ACYLATE COMPOUND HAVING THEAVERAGE GENERAL FORMULA (OALX)N, WHERE N IS 2-10 AND X IS AN ACYLATEGROUP OF THE FORMULA RCOO- WHERE R IS A HYDROCARBON RADICAL CONTAINING6-30 CARBON ATOMS, IN AN AMOUNT SUFFICIENT TO INCREASE THE INITIAL RATEOF COOLING OF SAID LUBRICATING OIL BASE.